A font is a set of displayable images, or “glyphs,” each of which depicts a letter, character or symbol. Each glyph can be thought of as the computer-age equivalent of a block of type used in a printing press. Developing a font is a skilled, labor intensive task. Typographers spend many hours crafting each glyph in a font, and consider not only the shape of the glyph itself, but also how the glyph will look in any likely combination with other glyphs. While developing a font for a single language is challenging, developing a single font that is supposed to cover multiple languages is even more difficult. For example, a font for plain English (US or UK) may need less than a hundred glyphs, but a font to support all scripts written with a Latin based alphabet requires thousands of glyphs. Similarly, basic typesetting of Arabic can be achieved with around a hundred glyphs, but setting all languages that are based on the Arabic writing system requires thousands of glyphs. Many other writing systems, such as Cyrillic, Greek, Hebrew and Thai, have also been used as the basis of extended glyph repertoires and thus provide a similar challenge in scale. Finally, although limited in variations, East Asian scripts, such as Chinese, Japanese and Korean, contain tens of thousands of glyphs. Thus, a truly international font requires of the order of 50,000 to 100,000 glyphs.
To conserve memory, many international fonts cut corners by, for example, using a single glyph for multiple written languages, even if the glyph is only appropriate for one language. For example, some East Asian ideographic characters are written differently by Chinese speakers than by Japanese speakers. However, the Unicode system, which forms the basis for many international fonts, often uses only one code for such characters. Thus, a typographer who is developing an international font may be forced to choose between constructing the Chinese version of a character or constructing the Japanese version of the character. Furthermore, there are often stylistic differences between Japanese and Chinese ideographs that are not accounted for by Unicode. This presents a similar problem for a typographer because even though the Chinese and Japanese versions of a particular ideograph might be the same in terms of number and arrangement of strokes, it is not necessarily appropriate to present a glyph from a Chinese font in a Japanese document, or vice versa.
A font developer might choose to build an international font by collecting glyphs together from several single writing system fonts, taking care to match the purpose of the international font and to keep the glyphs balanced in weight and size. When matching fonts for this purpose, a font developer may find that some groups of writing systems have more similarity than differences. For example, Latin, Greek and Cyrillic scripts share many features, such as upper and lower case letters, and the use of serifed and sans serif styles. In contrast, writing systems such as Arabic also have a huge variety of typographic styles, although none correspond so directly to other scripts as, for example, Latin and Cyrillic do. Thus when creating a range of international fonts for a variety of purposes, font developers may mix and match existing fonts in different ways, and even incorporate a font for a single writing system into several different international fonts. For example, the ‘Arial’ and ‘Times New Roman’ fonts used in MICROSOFT® products contain different Latin glyph sets, but use the same Arabic glyph set.
To summarize, international font developers face a variety of problems when using current font development techniques. One problem is that time is wasted constructing, testing maintaining the same glyphs into multiple fonts. Another problem is that, to match correctly in size, some glyph sets need resizing, which is usually an expensive process. Yet another problem is that glyph counts frequently exceed the maximum allowed by current font technologies (65536 for TrueType/OpenType). Finally, as the previous discussion indicates, representing the same glyphs in multiple fonts wastes memory.
Wasted memory is of particular concern in the context of printer fonts. Most of today's printers include built-in fonts. Thus, when using a printer font, a computer program need only send character codes to the printer, rather than sending entire glyphs. When using a font not included with the printer, however, the computer program also needs to download the font to the printer. This increases the size of temporary files created during the print process, the time needed to print the document at the client workstation, the time needed to transmit the document to the printer at the print server. It also consumes precious memory inside the printer.